It is planned to explore the structural basis of the physiological functions of the soluble, magnesium-dependent F1-ATPases which catalyze both the hydrolysis and synthesis of ATP. Many vital processes, such as the pumping of heart, the maintenance of ion gradients across nerve membranes, nutrient assimilation and waste elimination, and the biosyntheses required for growth and reproduction as well as for the normal metabolic control and turnover, depend on these enzymes for ATP supply. But in spite of the great deal of ingenious and careful research already done on these enzymes and their complexes with membrane components, we still know very little about the catalytic mechanism. Recently the amino acid sequences of the subunits of F1-ATPase and the Fo-components from E. coli have been determined in two other laboratories. With this new information on the primary structure of this enzyme, we plan to determine unambiguously the location of several essential functional groups in the beta-subunit and their relative topographical relationship by a selective labeling method with specific radioactive reagents, cleaving and isolating the labeled peptides, and locating the labeled residues by sequencing. We also plan to investigate the supposed regulatory sites on alpha subunits by examining the effect of removal of tightly bound adenine nucleotides from the alpha subunits on the chemical properties of the beta-subunit with its catalytic site and the gamma-subunit with its putative proton channel. In addition, attempts will be made to map the tight nucleotide binding sites on the alpha subunits.